Extending the admin menu (LH side)

My developers are constantly running into an issue where they have too many admin items in the LH main menu - potentially confusing the h*ll out of the client. What I have asked is that they group related functions into a group menu item eg. "Settings" or "Communication" etc.

Ideally, when a group tab is clicked it will expand to reveal further sub functions. Accordian style - but does not have to involve any complex Jquery.

Has anyone discovered a way of extending the default admin menu so that child lists could be inserted - as they have indicated this would be a major update? It seems a very simple concept to me??